Integrated photonic circuits are capable of integrating multiple photonic devices and components for various functions, such as transporting, focusing, multiplexing, demultiplexing, splitting, combining, polarizing, isolating, coupling, switching, filtering, modulating, detecting and generating light. Integrated photonic circuits may combine several of these functions onto a common chip or substrate. Photonic elements of photonic devices are typically silicon-based or silicon nitride-based. The photonic devices and components may be fabricated on a variety of substrates, including silicon.
Silicon-based photonics, however, may be very sensitive to temperature. For example, the sensitivity of silicon is typically about 100 GHz per degree Celsius. The sensitivity of silicon nitride is typically about several GHz per degree Celsius. Accordingly, a resonance frequency of silicon-based photonic elements (for example, optical waveguides and microresonators) may shift with variation in temperature. It is typically difficult to control thermal flow in micrometer-sized silicon-based photonic elements, because silicon is a good thermo-conductive material. Furthermore, because silicon is thermo-conductive, there may also be thermal-induced cross-talk between neighboring devices in the integrated circuit. Accordingly, it is desirable to stabilize the temperature of the photonic system.